I concur that there is no point in splitting your PNR to become upgrade eligible.

Not only are you an FO on V and X fares, which are Delta's lowest and second lowest cash booking classes respectively, you would presumably be splitting the PNR so that you and a member of your party would be together. In this case you would only be cleared for upgrades if you were #1 on the list for 2 or more seats. This is, as others have pointed out, extremely unlikely. If you were #1 for 1 seat and #2 was a party of one then #2 would get the upgrade. These scenarios are mostly hypothetical though, since out of ATL you could easily be #50 or deeper.